The invention concerns a tube holder for a tube filling machine, comprising a cup-shaped housing having a tube receptacle that opens towards the top and into which one end area of a tube can be inserted, wherein at least one vertical groove is formed in the area of the inner wall of the tube receptacle, into which a clamping element is inserted, wherein the clamping element can be radially displaced substantially perpendicularly with respect to the longitudinal central axis L of the tube receptacle, and is disposed to be pivotable about a pivot axis that extends substantially tangentially to the inner wall of the tube receptacle, wherein a clamping force that acts in a radial direction from the outside onto the inserted tube can be applied by the clamping element under the action of at least one spring element, wherein the clamping element has an upper first section which is disposed on the side of the pivot axis facing the opening of the tube receptacle above the pivot axis, and a lower second section which is disposed on the side of the pivot axis facing away from the opening of the tube receptacle below the pivot axis.
A tube filling machine of conventional construction has an endlessly revolving conveying device that carries a plurality of receptacles, into each of which one tube holder is inserted. The head or cap section of one tube can be inserted from the top into each tube holder, wherein the tube runs through the individual working stations of the tube filling machine together with the tube holder. In certain working stations, e.g. the filling station and the closing station, the tube including tube holder may be lifted out of the receptacle and inserted into the respective working station, wherein it is lowered again into the receptacle after termination of the working step. The filled and closed tube is removed from the tube holder in a removing station and transported away.
A tube holder in accordance with the German patent 1 173 862 comprises a cup-shaped housing with a tube receptacle which opens towards the top and into which the head or cap section of a tube, which preferably consists of plastic material or metal, is inserted. Several vertical slots are formed in the inner wall of the tube receptacle, which are distributed about the periphery of the tube wall. One clamping element is loosely fitted into each slot which is under the action of an outer spring element. Each clamping element is floatingly disposed and can therefore be adjusted perpendicularly with respect to the longitudinal central axis of the tube receptacle, and is loaded by the spring element in a radially inward direction towards the longitudinal central axis of the tube receptacle. When a tube is inserted into the tube receptacle, the tube urges the clamping elements in a radially outward direction against the respective spring force. The reaction force urges the clamping elements from the outside in a radial direction against the outer wall of the tube, thereby fixedly clamping the tube in the tube receptacle.
The terms “upper” and “lower” used in this description refer to the normal orientation of a tube holder with a tube receptacle that opens towards the top and into which the head or cap section of the tube can be inserted from the top, such that the end of the tube to be closed projects past the tube holder on the upper side. When the tube holder is oriented in this fashion, its longitudinal central axis extends in a vertical direction and the clamping elements are radially displaced in a direction perpendicular thereto, i.e. substantially horizontal.
The tubes change their geometrical shapes during passage through the tube filling machine. An empty, still unclosed tube has a cylindrical, in particular circular cylindrical, tube body. When the tube has been filled, it is closed. A plastic tube is closed by compressing the end of the tube facing away from the tube holder using closing jaws and welding it, thereby forming a linear weld seam that usually extends perpendicularly to the longitudinal axis of the tube. A metal tube is closed by compressing the end of the tube that faces away from the tube holder and folding the compressed tube end several times. The following example is based on a welded plastic tube. The invention is, however, not limited thereto.
When the tube is closed, it obtains a rotationally asymmetrical shape. As viewed from a direction perpendicular to the weld seam, the tube has a shape that diverges upwardly towards the end that comprises that weld seam. As viewed from a direction perpendicular thereto, the tube has a shape that converges towards the weld seam.
In order to adjust the orientation of the clamping elements to the tube shape in the respective peripheral tube area, the clamping elements in accordance with DE 1 193 862 are disposed to be freely floating, which permits pivoting of the clamping elements about a pivot axis that extends substantially tangentially relative to the inner tube wall of the tube receptacle. This is, however, disadvantageous in that the position of the pivot axis is not exactly defined but may be displaced in dependence on the position of the clamping element relative to the tube holder and also in dependence on the tube shape, such that retention of the tube in the tube holder cannot be exactly reproduced. Moreover, retention of the tube in the surface or peripheral areas that converge to the upper tube end in accordance with the tube holder of DE 1 193 862 is highly inadequate.
It is the underlying purpose of the invention to provide a tube holder of the above-mentioned type which reliably holds all peripheral areas of both an empty tube as well as a closed tube.